Lock rock

D

DocT

Joined
Mar 25, 2012
Messages
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My 50 year old 110 440C and my nearly 40 year old 425M 110 have almost no discernible lock rock when doing hard cutting. This is in spite of having been used hard. I have owned some very expensive back locks that have much more. The tolerances in these old 110s must have been pretty good.

How do the modern 110s stack up in this regard?
 
Every modern 110 I've handled has been rock solid. Ecolites, Maxlites, Bantams and Slimlines, not so much.
 
I've been wanting to ask this for awhile and this seems like a good thread to ask. Does lock rock matter on a knife? Does it stay at that same point of rock, or does it get worse and eventually fail? If it stayed at a little up and down movement, I could live with it if I knew that is all it would get. Hope that makes sense. I have an old case knife and it has some bad side to side wiggle, never even noticed it until I read about it on the blade forums and checked, and yep, lots of side to side.
Is there any way to take out lock rock? I can get all side to side out with a large C-clap.
 
jec88 said:
I've been wanting to ask this for awhile and this seems like a good thread to ask. Does lock rock matter on a knife? Does it stay at that same point of rock, or does it get worse and eventually fail? If it stayed at a little up and down movement, I could live with it if I knew that is all it would get. Hope that makes sense. I have an old case knife and it has some bad side to side wiggle, never even noticed it until I read about it on the blade forums and checked, and yep, lots of side to side.
Is there any way to take out lock rock? I can get all side to side out with a large C-clap.
Click to expand...

I think it all depends on the cause of the movement (in both questions).

Regarding the up and down play: It is possible through hard use to compress the piece of the lock bar that sits into the notch on the blade and increase the amount of up and down play, but that would take a significant amount of force to do. Otherwise, I can't see how it would get worse on it's own.

Regarding the side-to-side wiggle: you may very well be able to tighten that up with a clamp if it's just wiggling because it's pinned a little loose or because the pin has stretched a bit. However, if the wiggle is caused by something like the lock bar being wider than the blade then you're only going to make the lock stiff and the blade will still wiggle.
 
My understanding is that lock rock comes from four primary places.

The first is a design issue related to the angle of the faces on the blade and lockbar where they meet. If you look closely, you'll see that the face where they meet is not quite vertical. Hard cutting forces will "rock" the front of the lock bar up under hard cutting. (Aside: Cold Steel's Triad design puts a stop pin there, which eliminates this. Would be nice to see Buck incorporate that design.)



Second is a poor fit between the blade's indent and the lock bar face as byond described. Spyderco's Sal Glassner claims that use of more malleable fine-blankable steels for blades and lockbars contribute to lock rock. Over time, the first mode of rock can cause the second as the lockbar face deforms.

Third is worn blade and lockbar pivot pins. Several Buck mechanics have reported on this forum that replacing the lockbar and pins usually fixes the problem.

And a fourth cause is when holes that the pivot pins sit in deform or are too big to begin with. Buck has said the plastic framed lockbacks can open up over time and as many have reported, the heads of the blade pivots on the Spitfire/Slimline models will visibly move in the frame sometimes.
 
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i have a few handfuls of modern 110s and 112s and bantams and 486s etc. most have minor lock rock...few have a bit more than minor. a rare few are rock.solid.
 
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